Yes, I love purple. Why do I love purple? Because it is the perfect balance of warm and cold, red & blue, energetic to soothing. Purple can be so many different kinds of moods, colors, or flavors, just by changing the balance of its components.
My purple hair. Lots of people ask how I do it, so here ya go:
I have the gal who cuts my hair (Lisa at Solstice Salon in Mountain View) lift color out of my hair in small streaks; they're skinny and spaced out just like regular highlights except with color lifter (read: professional bleach) instead of hair color. (I doubt I'll ever be competent enough at hair stuff to do my own highlights; Lisa's amazing and I only go about once every 5 months, because her work is so good it looks great for that long.)
Then at home, I use Manic Panic. The flavor I use is called Purple Haze (the "amplified" version). I like Purple Haze because it produces a very layered set of purple tones; not a solid block of one purple shade. The color depth is *key* to making funky-colored hair look good (IMHO); multi-colored hair or one shade with tonal depth looks so much more awesome than hair that is all one flat color.
Application:
I wear gloves every time. I separate out the hair to be dyed and pull the rest into a low ponytail (all the bleached highlights are around the crown of my head, for easy access). I am very very generous with the amount of color I use when I put it on; I really slather it on thick. I don't use a brush -- I've tried, but I just end up dripping dye everywhere! My fingers are much more dexterous by themselves than they are holding a brush.
When I'm done purple-ing, I roll all the purpled hair into a little bun on my head and use ballet-style bun pins to lock it down. Then I put a plastic shower cap over my head and pin that down. Then I sleep with the color on. (On top of a purple pillowcase, just in case). In the morning, I rinse the purpled hair until the water runs clear, then use conditioner (no shampoo). Taa Daa! Rich purple hair.
The longer you can leave the color on (under plastic), the better the color "takes." If you can't leave it on overnight, you can encourage the chemical reaction with heat; put your hair in the shower cap and then use a hair dryer for as long as you can take it.
NOTE: If you are planning to color gray hair, be aware that gray hair is just harder to color. When it goes gray, it's losing its ability to hold on to color in general...so it won't hold hair dye as well. Some people say gray hair is easier to color with a peroxide or bleach treatment first, just like your regular colored hair. I haven't ever tried coloring gray hair, though, so ya don't have to take my word for it. (Oh Reading Rainbow, I miss you...)
I re-do my purple about every 3 weeks, sometimes 4. I do NOT wash my hair every day (that's bad for your hair, unless you swim every day and need to get the chlorine out). I wash my hair every ~3 days. If you are currently on a daily wash regimen, you'll need about a month of committed under-washing to get your scalp used to less oil production (don't bail on week 2 if you can't stand the grease!). But the extended wash cycle is such a blessing, especially for wavy/curly hair.